Active Noise Reduction (ANR) systems, particularly active control systems for headphones and earphones, are well known in the art. ANR techniques offer the capability to cancel (at least some useful portion of) unwanted external sound via feedforward control and/or to cancel excess pressures generated in the blocked (or “occluded”) ear canal during speech (“occlusion effect”) via feedback control.
ANR systems in the art are typically optimised for a particular architectural configuration according to one of a number of available choices of controlling topologies and processing technologies (e.g. analogue or digital). The architecture is internally defined by the internal hardwiring of the device and the processing is defined by the technology implemented in the device.
Typically ANR systems in the art vary in complexity, performance and power consumption depending upon the application for which they are designed. A manufacturer may have to produce a range of different devices to satisfy the needs of their customer base, with a variety of different technologies being implemented over the range of devices.